Bumping this again because the most recent updates haven't done a single thing to fix this problem. It never used to be an issue when I used Spotify while driving for the past 3 years I've used this service. Tried to mess around with the settings in the Spotify app and within my iOS but to no avail. Would be a shame for this issue to be permanent. As another comment mentioned above, using the Guided access works as a temporary fix. But it's a completely unnecessary and inconvenient step to take. There's 5 pages of people talking about the same thing happening to them, so I'm not sure how much more information is needed to revert this problem back to the way it was before.
Re: iPhone screen locking while playing and connected to charger - Status changed to: Under investigation